It is extremely important in the manufacturing of disposable containers to maximize use of the container material. The bottom of a container is usually severed from a continuous web, thus incurring waste in the area of the continuous web between the severed blanks.
To maximizing the use of the container material it is extremely essential that the bottom blanks be severed in close proximity to each other along the length of the continuous bottom blank web. Further, the cylindrical blanks which define the side walls of the container must also be severed from a second supply of material in such a manner to maximize use of the container material.
Apparatus for cutting and transferring bottom blanks from a continuous web should continuously transfer the severed bottom blank to the final forming mandrel or other work station at which the blank is to be utilized and at the same time minimize the waste of the bottom blank material web. Final forming mandrels utilized in the construction of disposable cups, for example, may be positioned along an endless chain and spaced from each other by a substantial distance. To minimize the waste of the bottom blank material web it is essential that the bottom blanks be severed in close proximity to each other. This gives rise to incompatible parameters, namely, a minimum spacing at the cutting station and a maximum spacing at the work station. As a consequence, there is a velocity disparity as well in a continuous feeding and forming process between web velocity at the cutter and the velocity of the transitory mandrels or other bottom blank receiving means at the work station at the point of transfer.
Further, it is known in the art to shrink form containers such as drinking cups from preformed tubular lengths of circumferentially oriented thermoplastic material such as foamed polystyrene.
One particularly desirable method of initially forming a tubular length of such circumferentially oriented material is to provide rectangular-preprinted blanks and wrap these blanks around a mandrel whereon a heat sealed seam is effected longitudinally along the circumference of the formed tubular length. The use of rectangular blanks facilitates pre-printing of patterns, designs, logos, etc., on the blanks such that the ultimate tubular lengths and containers formed therefrom will bear the ultimately desired indicia.
A further advantage of the rectangular blank is that it may be cut from an extruded sheet of thermoplastic or thermoplastic foam which is streched longitudinally, i.e., in the most logical, natural and facile direction of stretch after extrusion, namely, the machine direction, to achieve the necessary circumferential orientation in a tubular length or cylinder formed from the rectangular blank.
Previous efforts to handle these rectangular blanks and form them into cylinders, however, have required relatively elaborate systems of transfer rollers, turrets with multiple mandrels thereon and vacuum systems to properly index leading and/or trailing edges of the rectangular blanks on the transfer rollers or mandrels.